This invention relates generally to the detection and analysis of contaminants in particulate matter, such as soil.
Contaminants such as heavy metal particles in soil are presently detected by methods involving chemical analysis, radiation measurement techniques and microscopic examination. In chemical analysis methods, metal contaminants are dissolved within solutions from which data on the overall percentage of the heavy metal in the soil is obtained by quantitative analysis. In the case of radiation measurement methods, the approximate overall percentage of radiation particles (such as uranium or plutonium) in a soil sample is obtained. The use of electron or optical microscopic examination on the other hand requires prior complete physical separation of the contaminant particles from the soil, involving soil washing or the use of a fluid medium to differentially accelerate movement of the soil and contaminants.
None of the foregoing prior art methods have the capability of providing data on contaminant particle size, geometry and distribution within soil samples. U.S. Pat. No. 4,783,253 to Ayres et al. relates, by way of example, to the separation of particles from soil contaminated by radioactive metals, but relies on prior soil treatment with water thereby foreclosing non-destructive analysis of soil samples to obtain data on size and distribution of contaminant particles therein.
The use of X-ray radiation techniques to detect and analyze contamination of soil or the like is generally known, as disclosed for example in U.S. Pat. Nos. 4,710,946 and 5,058,425 to Hinch et al. and Davis, Jr., et al., respectively. The method disclosed in the Hinch et al., patent is, however, limited to X-ray examination of solid core types of rock samples precluding detection of particles within a small size range (below 1 mm for example). A complete analysis of soil samples with respect to both size and distribution of all contaminant particles therein is therefore not possible through use of the method disclosed in the Hinch et al. patent. Detection and analysis of soil samples with respect to contaminant particle size and distribution is also precluded by the method disclosed in the Davis, Jr. et al. patent, involving treatment of a core of coal to detect its methane storage capacity.
It is therefore an important object of the .present invention to provide an improved, non-destructive method of analyzing particulate matter with respect to size and distribution of solid contaminants therein.
In accordance with the foregoing object, the present invention is particularly useful in obtaining data on the size and location of heavy metal contaminants in soil for various purposes, including but not limited to controlling the physical separation of such contaminants from the soil in a more efficient and less costly manner.